The invention relates to a safety coupling for a motor vehicle.
In electric vehicles or hybrid vehicles that use an electric machine as driving engine the electric machine is often inseparably connected with the drive wheels, i.e, there is no coupling between the electric machine and the driving wheels but for example only a positive force transmission element such as a cardan shaft or a transmission. When an error occurs in the electric machine or in the power electronics in such a rigid drive connection or when the power electronics is switched to an active short circuit for generating a safe vehicle state, very high torque peaks can occur for a short time which significantly exceed the nominal torque of the motor and can vibrate with high frequency. Such a torque peak can have triple the value of the nominal motor torque, which may render the motor vehicle instable with regard to driving dynamics. The tires of the drive wheels, which are rigidly coupled with the electric machine via the drive train, may thereby lose their grip on the street.
In principle, it is possible to integrate elastic intermediate elements into the drive train in order to decrease the torque peak in case of a malfunction. This elasticity in the drive train however has adverse effects during normal operation, because the positive characteristic of the electric machine, namely a fast torque buildup, can no longer be optimally used. In addition, the elastic intermediate elements also render the drive train more prone to interfering vibration during normal operation.